There are numerous applications for embedded microprocessor devices. These applications may include various technologies for cellular telephones, notebook computers, handheld computers, personal digital assistants, automobiles, appliances and other consumer products. For example, a cellular phone may have an embedded general applications processor and a baseband processor. Typically, the applications processor may manage database applications while the baseband processor may support a communications platform such as General Packet Radio Service (GPRS) or Code Division Multiple Access (CDMA).
The number of microprocessors that are being embedded into devices, particularly handheld devices, is increasing to provide customers with additional features. These new features have increased the types and amounts of data embedded processors exchange with other microprocessors, peripherals and/or external servers. For example, embedded microprocessors now exchange everything from command and control data to large databases and streaming data for voice and video communications.
In the past, if there was a need for inter-processor communications, these communications could be accomplished through a low-speed physical link, such as a serial interface, which may have limited quality of service (QoS) and data reliability management. However, today's designers are integrating new features into handheld devices such as CMOS digital imaging, World Wide Web (WWW) access and multimedia processing. In addition, handheld devices are also supporting more recent communications platforms such as Wideband Code Division Multiple Access (WCDMA), IEEE 802.11, Bluetooth® and the like for next generation wireless applications. This expansion of capabilities has led to the emergence of handheld devices that are structured more like personal computers. For example, these devices might include an applications subsystem for implementing various database and multimedia applications and then separate communications subsystems for implementing wireless communications.
Separate processor subsystems have necessitated an increased focus by circuit designers on high-speed processor to processor communications. Recently, particular attention has been paid to providing a high-speed, reliable standard for a communications interface between an embedded general purpose applications processor and a baseband processor. One example of a high-speed processor to processor communications interface is Intel® Corporation's Mobile Scalable Link® (MSL) technology. Factors considered for an inter-processor communications standard may include high inter-processor data transmission rates, scalability for increasing bandwidth, QoS, security, and the elimination of data exchange bottlenecks. Unlike the typical personal computer, however, these devices have to be designed with severe packaging and power consumption constraints in mind.